Process for cleaning ceramic articles

ABSTRACT

A method for cleaning ceramic workpieces such as SiC boats used in semiconductor fabrication is disclosed. The method comprises washing a virgin or used ceramic workpiece with a strong acid and then using a pelletized CO 2  cleaning process on the acid-washed component. The inventive method has been found to produce a workpiece having a very low level of metallic and particulate contaminants on its surface.

FIELD OF THE INVENTION

[0001] The present invention relates to methods for cleaning ceramicarticles. More particularly, the present invention relates to method forremoving both particle impurities and chemical impurities from ceramicarticles used in the manufacture of semiconductor devices.

BACKGROUND OF THE INVENTION

[0002] The manufacture of semiconductor devices typically requiressubjecting the surface of a silicon wafer to high temperature processessuch as diffusion, oxidation and deposition. In deposition processes,dielectric materials such as polycrystalline silicon, silicon nitrideand silicon dioxide are deposited on the surface of the wafer. Indiffusion processes, materials are diffused into the body of the siliconwafer. In oxidation processes, the surface of the wafer is oxidized toform a thin silica layer. Each of these processes typically involvesplacing the wafers to be processed in a holder, often called a “boat”.The boat is typically formed of a ceramic material and is configured tohold the wafer in either a horizontal or a vertical orientation. Onceloaded with wafers to be processed, the boat is placed in anelectrically-heated furnace or process tube, and then the environmentinside the tube is altered to provide various atmospheres havingtemperatures typically ranging from 250° C. to over 1200° C.

[0003] Another common semiconductor process is etching. After aphotolithographic pattern is deposited on the surface of a siliconwafer, the wafer is loaded into an etcher. The etcher, whose componentsare typically made of a ceramic material, uses a plasma etching processto remove the materials deposited on the wafer surface which are notprotected by a photolithographic pattern. The typical etching processremoves oxides, metals and/or polymers from the wafer surface.

[0004] Although each of the processes described above successfullydevelops the surface of the silicon wafer into a useable product, theyalso eventually contaminate the surfaces of the supporting equipment aswell. For example, a nitride deposition process will leave a coating ofsilicon nitride upon not only the wafer, but also upon the surface ofthe boat which supported the wafer during the deposition process. Whenthis coating becomes too thick, it tends to flake and contaminate nearbywafers with particles.

[0005] In an etching process, the deliberate removal of various layersof material from the wafer-in-process can cause contaminant particlessuch as silica, nitrides, and alumina to be deposited on the surface ofetcher components. Since contaminants adversely affect the processing offuture wafers to be processed by these components, contaminant particlesmust be carefully cleaned from the surfaces of these components. Becauseof the decreasing line widths of silicon wafers, it has becomeincreasingly important to remove more sub-micron particles from thesurface of these components, more particularly sub-micron particleshaving a width of no more than 0.7 microns.

[0006] Several methods for cleaning used ceramic boats are known in theprior art. In one method, a used component which is coated with adeposited material such as silicon nitride, polysilicon or silicaundergoes a two-step cleaning process whereby the component is firstexposed to a stream of hard pellets, such as silicon carbide pellets, ina process akin to sand-blasting, and then to a stream of frozen carbondioxide (CO₂) pellets. The first step, termed preliminary cleaning,successfully strips deposited material from the component surface,leaving behind some debris particles on the order of one micron. In thesecond step, termed primary cleaning, the frozen CO₂ pellets arebelieved to cause the micro-sized debris particles to freeze, therebybecoming brittle, and then break, thereby allowing them to be easilyflushed from the surface.

[0007] Preliminary cleaning is ordinarily carried out either byimpinging or “blasting” glass, aluminum oxide, silicon carbide, titaniumoxide, walnut shell particles, or other hard beads against the partbeing cleaned. The beads are typically carried in a pressurized streamof air or other gas. The beads,can be spherical, granular, or any otherdesired shape and dimension. One commonly used bead material is 98%black SiC grit. The pressure under which the beads are directed to thesurface depends on the composition of the part being cleaned. When aceramic part is to be cleaned, the beads typically are applied in a gasat a pressure in the range of about 20-35 psi. Once completed, the beadblasting, preliminary cleaning, step is followed by a CO₂ cleaningprocess. CO02 cleaning processes have been described in the patentliterature. See, for example, U.S. Pat. No. 4,707,951, entitled“Installation for the Projection of Particles of Dry Ice”.

[0008] In another method of cleaning a used boat which is coated withdeposition layers, one manufacturer recommends subjecting the used boatto an acid treatment, preferably using a strong acid such as HF,followed by baking. This HF treatment removes the deposited layer ofmaterial.

[0009] The cleanliness of virgin semiconductor processing equipment hasalso been a concern in the art. However, for a virgin part, the concernhas typically been metallic, rather than particulate, contamination. Inone conventional method of manufacturing SiC diffusion components, thevirgin SiC diffusion components are subjected to a weak acid and thenbaked. This process serves to remove some metallic contaminants andfingerprints from the part being cleaned.

[0010] In another conventional method of insuring the cleanliness ofvirgin components, the component is subjected to a strong acid such asHF prior to installing it in a furnace. Similarly, hot HCl cleaning hasbeen used in connection with semiconductor diffusion components. Forexample, in UK Patent Application No. GB 2,130,192, the investigatorsdisclose a manufacturing step of subjecting a virgin SiC component tohot HCl treatments prior to use in a semiconductor furnace.

[0011] In some cases, HF treatment by itself has been consideredsufficient for cleaning both virgin boats (to reduce metalliccontamination) and used boats (to chemically strip coatings depositedduring semiconductor processing). That notwithstanding, the use of HFalone fails to remove problematic debris particles that may still bepresent after such treatment.

[0012] In sum, conventional methods of providing a clean virginsemiconductor component involve acid cleaning to remove metalliccontamination, while conventional methods of cleaning used componentsinvolve either i) a two-step process of mechanical stripping ofdeposited coats via bead blasting followed by CO₂ cleaning to removesmall debris particles, or ii) hot strong acid cleaning to remove a coatof deposited material.

SUMMARY OF THE INVENTION

[0013] The fabrication of semiconductor devices requires the use ofprocess components having a high level of surface purity, whether thosecomponents are new or reconditioned. In certain workpieces, such asceramic boats used to position and maintain semiconductor wafers duringprocessing, the long depth and narrow spacing of the wafer-retainingslots define a boat geometry with a contoured surface having an aspectratio that prevents bead blasting from sufficiently stripping coatingsfrom the deeper portions of these slots. In particular, aspect ratios,(i.e., the ratio of slot depth to slot width), of greater than about 4:1are typically beyond the ability of conventional cleaning methods. Thepresent invention presents a method for overcoming this and othershortcomings by providing a process in which the inorganic surface ofsemiconductor fabrication components is cleaned by chemical strippingfollowed by CO₂ cleaning. In one embodiment, the chemical stripping iscarried out using a solvent containing a strong acid. In a morepreferred embodiment, the chemical stripping is carried out using asolvent having at least 1 v/o of an acid selected from the groupconsisting of HF, acids having a pKa of less than about one, andmixtures thereof. As used herein, “v/o” represents a volume percent, and“strong acid” represents a solution having at least 1 v/o of an acidhaving a pKa of less than about one.

[0014] The CO₂ cleaning step employs particles of dry ice which areprojected against the surface being cleaned. The combination of thechemical stripping and the CO₂ cleaning step has been found tosuccessfully remove both particulate and metallic contaminants from thesurface of the workpiece.

[0015] Workpieces cleaned using the inventive process have been found tohave a surface contaminant particle density of no more than about 0.4particles, and preferably no more than about 0.2 particles, larger thanabout 0.3 μm per square centimeter. Such workpieces have also been foundto have a surface metallic contaminant concentration of no more thanabout 600 ppm, as measured by SIMS at a depth of about 10 nm. Of thesurface metallic contamination, no more than about 400 ppm of metalcontaminants other than alkaline and alkaline earth metals, and no morethan about 225 ppm of iron, (as measured by SIMS at a depth of about 10nm), remain following application of the inventive cleaning process totypical workpieces.

[0016] The present invention is based upon the recognition thatproblematic debris particles may still be present after HF treatment,and that CO₂ cleaning steps, while removing particulate contaminants,are unable to remove non-particulate metallic contaminants. To date, theart has lacked any suggestion of the present invention which employs HFtreatment to remove metallics followed by a CO₂ cleaning step to removeany remaining debris particles. Combining a CO₂ cleaning step with HFtreatment is unique in that CO₂ cleaning has traditionally been usedonly after a used workpiece underwent mechanical stripping whichproduced debris particles.

[0017] The present invention also relates to workpieces, such as ceramicboats used in semiconductor processing, that have been cleaned using theprocess of the present invention. The resulting workpieces are unique inthat their level of metallic and particulate surface contamination issignificantly below that which has previously been obtainable usingprocesses known to those skilled in the art.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention provides a process for providing ceramicworkpieces, such a ceramic boats used in semiconductor fabrication witha lower level of metallic and particulate surface contamination than haspreviously been available. Specifically, whereas it is known in the artto use acid cleaning, and whereas it is also known in the art to usebead-blast cleaning in combination with CO₂ cleaning, to date, there hasbeen no suggestion in the art to combine an acid cleaning step with aCO₂ cleaning step for cleaning either virgin or used, coated ceramicworkpieces. The recognition that an acid cleaning step can be combinedwith a CO₂ cleaning step yields a cleaning process that is well-suitedfor use with both virgin and used, coated workpieces.

[0019] As noted above, use of the inventive process has providedworkpieces having a surface contaminant particle density of no more thanabout 0.4 particles larger than about 0.3 μm per square centimeter, anda surface metallic contaminant concentration of no more than about 600ppm, as measured by SIMS at a depth of about 10 nm.

[0020] Traditionally, upon receiving a virgin workpiece such as aceramic boat from a manufacturer, the user would subject the workpieceto an acid cleaning process in order to remove any metallic contaminantsthat may have deposited on the workpiece during manufacture, packaging,shipping, etc. In some instances, used, coated workpieces would becleaned by chemical stripping using a strong acid. As with the virginworkpieces, the acid cleaning provided a satisfactory means for removingmetallic contaminants form the surface of the workpiece.

[0021] Although acid cleaning provides a surface having metalliccontaminants lowered to satisfactory levels, the process fails toprovide a surface having a sufficiently low level of particulatecontamination. In fact, some evidence exists that the acid cleaning stepactually contributes to particulate contamination. Without wishing to betied to any particular theory, in cleaning a workpiece such as a usedceramic boat, workpieces cleaned using HF to chemically strip a coatingstill have a high level of particulate contamination because thestripping process leaves particulate contaminants on the ceramicsurface.

[0022] Furthernore, particulate contamination does not result solelyfrom the acid cleaning process and post-processing steps. Rather, in thecase of virgin workpieces, it is believed that machining the component,such as an SiC boat, produces particles which deposit upon the surfaceof the component. Of course, particles also may deposit upon a virgincomponent because of exposure of such components to non-clean-roomenvironments. It should be noted that, in the case of either virgin orused components, and pre-processing, processing or post-processingsteps, many mechanisms for the formation of particles on the workpiecemay exist, and the present invention is not intended to be limited toany particular particle formation or deposition mechanism.

[0023] As noted previously, CO₂ cleaning procedures have traditionallybeen used in combination with a preliminary cleaning step such asbead-blasting. The combination of bead-blasting and CO₂ cleaning hasgenerally not been used on virgin workpieces, but rather, has beenemployed on used workpieces that have had CVD coatings deposited ontheir surfaces during semiconductor processing. While this method hasbeen found to be satisfactory for the removal of particulatecontaminants, it lacks the ability to remove metallic contamination thatoccurs on both virgin and used workpieces.

[0024] The present invention recognizes that until the workpiece, be ita virgin component or a chemically-stripped component, is subjected to afinal CO₂ cleaning step, problematic submicron particles which need tobe eliminated from the surface of the components will remain. The needfor removal of such particulate contaminants, as well as the manner inwhich such removal is achieved is neither appreciated nor performed inconventional processes.

[0025] Moreover, it appears that products resulting from the inventiveprocess also possess superior levels of metallic purity as compared tore-worked products processed by cleaning methods which use CO₂ cleaningto clean the used coated workpieces. As noted above, one conventionalprocess mechanically strips the coating from a used component, such as aboat, via bead blasting, and then uses CO₂ cleaning to complete thecleaning. Without wishing to be tied to any particular theory, in thecase of a used boat, the conventional understanding is that surfacemetallic contamination is not a problem. Conversely, even if surfacemetallic contamination did give rise to problems, it was wrongly assumedthat such problems could be sufficiently eliminated using techniquesknown in the prior art.

[0026] In contrast, some evidence suggests that a bead blasting stepactually acts to increase the concentration of metallic impurities atthe surface of the workpiece. This undesirable effect may be the resultof the use of impure blasting media.

[0027] The process of the present invention is superior to theconventional bead blasting/CO₂ cleaning process in that it does notresult in metallic contamination of the surface of the strippedworkpiece. In fact, the present inventive process acts to reduce theconcentration of metals at the surface.

[0028] Likewise, for a virgin workpiece, such as an unused SiC boat, theconventional understanding of surface metallic impurity has been that HFor hot HCl cleaning offered only marginal utility because it served onlyto incrementally reduce the concentration of metals at the surface ofthe component to a level slightly below that of the bulk materialforming the workpiece (1 - 10 ppm for SiC), and that this relativepurity advantage over the bulk disappeared over time as subsequent useunder high temperature environments promoted the diffusion of bulkmetals into the surface region of the component. Accordingly, the artdid not require HF cleaning in all circumstances.

[0029] The surface of materials representing virgin SiC components hasbeen analyzed by one conventional method (x-ray photoelectronspectroscopy, referred to herein as XPS) and by another method(secondary ion mass spectroscopy, referred to herein as SIMS). Aconventional XPS analysis provides information at a depth of about 3 nmand has a sensitivity of about 0.1-1.0% depending upon the element ofinterest. In contrast, the SIMS analysis can provide information at adepth of about 10 nm and has a sensitivity of about 0.2-3.0 ppm. Forthis reason, the SIMS test provides a more accurate method for measuringthe surface concentration of metals in semiconductor processingcomponents. It has been found that in instances where XPS failed todetect any metals, (and thus failed to provide any indication of anelevated surface metals concentration), the SIMS test reported about2000 ppm metals at a depth of 10 nm. In the field of high temperaturesemiconductor processing, these surface levels are clearly undesirable.Accordingly, as a result of the SIMS analysis, there is now ademonstrated need to clean the surface of a virgin ceramic component,preferably using a strong acid solution, in order to reduce the highsurface level of metallic contaminants present at the surface ofsemiconductor processing components. It should be appreciated that, inone embodiment of the present invention, the surface is a CVD surface,which optionally may have been subjected to machining or otherpost-processing steps.

[0030] More particularly, it should be understood that the process ofthe present invention is intended to be applied to a wide variety ofinorganic surfaces employed by semiconductor processing components. Suchsurfaces typically comprise ceramic materials such as those ceramicscommonly used in semiconductor fabrication, however, the process may beapplied to non-ceramic surfaces such as silicon and diamond as well.Thus, while the discussion has focussed primarily on semiconductorprocessing components such as ceramic boats, and particularly thoseformed of SiC, it should be understood that the invention is notintended to be limited in this manner. Rather, the invention is intendedto apply to any of the semiconductor processing components that haveinorganic surfaces associated with semiconductor wafer processingtechniques. These surfaces include, but are not limited to silicon (Si),silicon carbide (SiC), silicon nitride (Si₃N₄), diamond, yttria (Y₂ O₃),zirconia (ZrO₂), aluminum nitride (AlN), aluminum oxide (Al₂O₃) andquartz.

[0031] The surfaces may be vapor-deposited, and as discussed above maybe deposited using CVD techniques. Such surfaces include, but are notlimited to polycrystalline or other CVD Si, CVD SiC, CVD SiO₂, CVD Si₃N₄and CVD diamond surfaces. Of course, it should be understood thatdespite the applicability of the present invention to surfaces havinginorganic coatings thereon, the process may also be applied to uncoated,inorganic surfaces.

[0032] In considering SiC workpieces, several varieties are used in theart. In one embodiment, a workpiece formed simply of SiC is used. Inanother embodiment, the workpiece comprises a reduced porosity SiCformed by loading the pores of a SiC structure with Si. Because thesilicon tends to escape from the pores, such workpieces are oftenprovided with a CVD SiC layer. More specifically, these componentstypically are formed of a porous α-SiC body having Si occupying thepores. To prevent the Si from escaping, a layer of very pure β-SiC isdeposited on the surface of the component using CVD methods. The β-SiCis intended to seal the surface and inhibit loss of Si near the surfaceof the workpiece.

[0033] It should be understood that the β-SiC material deposited on theworkpiece to prevent Si from escaping is not intended to be removed bythe process of the present invention. Rather, when referring herein tothe removal of coatings from used workpieces, the subject coatings arethose that have been deposited on the workpiece during its use insemiconductor processing. Thus, a virgin coated workpiece refers to anewly manufactured workpiece having a desired coating formed thereon,while a used, coated workpiece refers to a workpiece having an undesiredcoating deposited during semiconductor processing. Of course, upon use,the virgin coated workpiece acquires an additional, undesired coating,and it is the removal of the coating which forms one embodiment of thepresent invention.

[0034] While useful with vertical racks, it should be understood thatthe process of the present invention employing a strong acid cleanfollowed by a CO₂ clean provides unexpected benefits not only forvertical racks, but also for semiconductor processing equipment of anyshape. Examples of semiconductor processing components used in singlewafer processing to which the present invention may be applied include,but are not limited to, bell jars, electrostatic chucks, focus rings,shadow rings, chambers, susceptors, lift pins, domes, end effectors,liners, supports, injector ports, manometer ports, wafer insertpassages, screen plates, heaters, and vacuum chucks. Examples ofsemiconductor processing components used in batch processing to whichthe present invention may be applied include, but are not limited to,paddles, process tubes, wafer boats, liners, pedestals, long boats, anddummy wafers. Examples of semiconductor processing components used inchemical mechanical polishing (CMP) to which the present invention maybe applied include, but are not limited to, conditioning pads and waferholders.

[0035] Lastly, it is believed that the process of the present inventionprovides for the first time a ready-to-install product, that is, aproduct that can be safely taken out of a protective shipping bag at theuser's facility and directly installed in a semiconductor furnacewithout any further cleaning by the user. This is achievable becausesuch components already have the lowest possible amounts of surfacemetals and particles achievable by surface treatments.

[0036] More particularly, in one aspect of the present invention,immediately upon completing the CO₂ cleaning step, the cleaned workpieceis installed either into a furnace used for processing semiconductorwafers, or into a bag used for the shipping and storage of cleanedsemiconductor processing components. In the former process, theworkpiece is transferred directly from CO₂ cleaning into the furnacewithout any further cleaning steps. In the latter process, the workpieceis packaged, i.e., bagged, directly following CO₂ cleaning without anyfurther cleaning steps. In this latter case, upon removing the workpiecefrom its packaging, it is installed directly into a furnace used forprocessing semiconductor wafers without any further cleaning steps.Unlike processes known in the art in which it is necessary to provideadditional cleaning steps between removal of the workpiece from itspackaging and installation in the furnace, components cleaned using themethod of the present invention may be installed into the furnaceimmediately upon removal from their packaging. This is advantageous inthat it eliminates additional processing steps which can, among otherthings, actually lead to increased levels of contamination, particularlyparticulate contamination.

[0037] Although several prior art cleaning regimes, and their advantagesand disadvantages, have been described previously herein, none of thoseknown in the art offer the ability to provide a surface having the lowcontamination level of metallics and particles available from theinventive process described herein. Washing in a strong acid solution,such as a solution containing HF or other acid having a pKa of less thanabout one, provides a surface having unsatisfactory levels ofparticulate contaminants. Alternatively, washing in a weak acid solutionor bead-blasting followed by a CO₂ cleaning results in less desirablelevels of metallic contaminants. It was not until the present invention,in which a strong acid cleaning is followed by CO₂ cleaning, that onecould achieve acceptable levels of both metallic and particulatecontamination.

[0038] In another embodiment of the present invention, the acid cleaningand CO₂ cleaning steps are coupled with a modified bead blasting step.Specifically, in this embodiment, the invention includes the steps ofbead-blasting the surface of the workpiece using green SiC particles.Subsequently, the surface is contacted with a solvent having at least 1v/o of an acid selected from the group consisting of HF, acids having apKa of less than about one, and mixtures thereof. The surface is thentreated using CO₂ cleaning. The use of green SiC in the bead-blastingstep is unique in that, to date, only black SiC has been used forbead-blasting purposes. In the present invention it has been found thatbead-blasting using green SiC beads provides surfaces that aresignificantly lower in contaminants. This is believed to be the resultof the composition of the black SiC beads versus the green SiC beads.Whereas the former comprise a grit containing about 98% SiC, (and animpurity level of about 2%), the latter contain impurities in the rangeof approximately 1000-2000 parts per million, (i.e., 0.1-0.2%impurities).

[0039] In still another embodiment of the present invention, the strongacid step can be eliminated entirely and replaced with a bead blastingstep using green SiC beads described above. Thus, the process employsthe steps of bead-blasting with green SiC followed by a CO₂ cleaning.

[0040] In yet another embodiment, the use of an acid cleaning step canbe eliminated when cleaning certain components. Specifically, as notedabove, certain workpieces may be provided with coatings. Such coatingsmay be provided by any of a wide variety of processes including chemicalvapor deposition, sputter deposition and spray coating. For example, aworkpiece formed of α-SiC may be provided with a CVD deposited β-SiCcoating to form a very pure surface. Likewise, thick CVD deposited SiCfilms of up to about 500 microns in thickness usually do not requireadditional machining steps, and thus avoid one significant source ofmetallic contamination. Alternatively, workpieces formed from otherceramic materials may be such that they do not require certainprocessing steps, such as sandblasting, that introduce metallicimpurities onto the ceramic surface. These workpieces also have surfacesthat are low in metallic contaminants. New workpieces having such coatedor otherwise pure surfaces are relatively free of metallic contaminants.Of course, any of the surfaces described above will include some lowlevel of unavoidable metallic impurities, however, such impurity levelsare significantly lower than those introduced by machining steps such assandblasting. As such, these workpieces can be cleaned using only theCO₂ process and installed directly into a furnace or immediatelypackaged without any additional cleaning steps. Likewise, the packagedworkpieces of this type can be removed from their packaging and directlyinstalled into a furnace without any additional cleaning steps. Thus,although the prior art includes processes in which the CO₂ process isused without an acid cleaning step, none of these processes are used inconnection with virgin workpieces of the type described above. Byeliminating the acid cleaning step for certain virgin workpieces,cleaning time and process complexity can be minimized.

[0041] It is noted that in each of the embodiments employing green SiCdescribed above, the CO₂ cleaning step may employ techniques andapparatus that are known in the art. One example of a satisfactory CO₂method and delivery system is that described in U.S. Pat. applicationSer. No. 08/890,116, entitled “Carbon Dioxide Cleaning Process”, theteachings of which are incorporated herein by reference.

[0042] Further improvements include the use of high purity CO₂ in theCO₂ cleaning step and the application of the present process, to theextent possible, in a clean-room environment. Needless to say, anyreduction in impurities in the environment surrounding the workpieceduring or after cleaning will result, ultimately, in a cleanerworkpiece.

EXAMPLES

[0043] Results are presented below for several tests of the steps usedin the inventive process. In Table 1, CVD SiC coated parts that had beensubjected to machining (i.e., wet or dry sandblasting) were analyzed formetallic impurities. These samples were measured either directly afterthe sandblasting, after a post-sandblasting weak acid treatment, orafter the samples had been subjected to the inventive process (HF/CO₂)post-sandblasting. The ability of the inventive process to provideimproved metal removal, particularly for iron can be seen in the Table.TABLE 1 Metalllic Impurities in Parts Per Million PROCESS Na Al Ti V CrFe Ni WS 6 54 3 0.5 14 115 2 WS 6 33 1 0.1 8 38 0.8 weak acid WS 2 17 10.05 6 28 2 Invention DS 136 98 60 10 4 1441 18 DS 132 60 39 7 3 381 8weak acid DS 7 107 20 3 4 211 4 Invention

[0044] Table 2 presents particulate impurity data for non-machinedsamples that do not have CVD coated surfaces. Samples 1-6 were treatedwith conventional workpiece cleaning steps, and samples 7-10 werecleaned using the process of the present invention. The numbers ofparticulate impurities are presented for two sides of each sample. TABLE2 Particulate Impurities I Sample Process Side 1 Side 2 1 Conventional0.98 1.12 2 Conventional 0.8 0.67 3 Conventional 0.77 0.78 4Conventional 0.99 0.86 5 Conventional 1.34 1.23 6 Conventional 0.79 0.867 CO₂ 0.03 0.17 8 CO₂ 0.14 0.12 9 CO₂ 0.05 0.03 10 CO₂ 0.04 0.12

[0045] Table 3 presents particulate impurity data for samples before andafter treatment with the CO₂ process described above. In samples A, Band C, the sample is machined SiC that does not have a CVD coating onits surface. Sample D is a non-machined sample having a CVD SiC surface.As can be seen, the use of the CO₂ process significantly reduces theamount of particulate contaminants. TABLE 3 Particulate Impurities IISample Particles Before Particles After A 0.35 0.04 B 0.54 0.13 C 0.550.09 D 0.65 0.01

EQUIVALENTS

[0046] From the foregoing detailed description of the specificembodiments of the invention, it should be apparent that a novel systemfor removing metallic and particulate contaminants from ceramicworkpieces has been described. Although particular embodiments have beendisclosed herein in detail, this has been done by way of example forpurposes of illustration only, and is not intended to be limiting withrespect to the scope of the appended claims which follow. In particular,it is contemplated by the inventors that various substitutions,alterations, and modifications may be made to the invention withoutdeparting from the spirit and scope of the invention as defined by theclaims.

We claim:
 1. A semiconductor processing component having an inorganicsurface, the inorganic surface having at most about 0.4 particles largerthan about 0.3 μm per square centimeter, and having a surface metalliccontaminant concentration of at most about 600 ppm, as measured by SIMSat a depth of about 10 nm.
 2. A semiconductor processing componenthaving an inorganic surface, the inorganic surface having at most about0.4 particles larger than about 0.3 μm per square centimeter, and havinga surface concentration of metal contaminants other than alkaline andalkaline earth metals of at most about 400 ppm, as measured by SIMS at adepth of about 10 mn.
 3. A semiconductor processing component having aninorganic surface, the inorganic surface having at most about 0.4particles larger than about 0.3 μm per square centimeter, and having asurface iron contaminant concentration of at most about 225 ppm, asmeasured by SIMS at a depth of about 10 nm.
 4. A semiconductorprocessing component as in any of claims 1-3, wherein the inorganicsurface is formed by chemical vapor deposition.
 5. A semiconductorprocessing component as in any of claims 1-3, wherein the inorganicsurface lacks a CVD coating.
 6. A semiconductor processing component asin any of claims 1-3, wherein the inorganic surface is a contouredsurface.
 7. A semiconductor processing component as in any of claims1-3, wherein the inorganic surface is a contoured surface including atleast one region having an aspect ratio of at least 4:1.
 8. Asemiconductor processing component as in any of claims 1-3, whichcomprises a bell jar, electrostatic chuck, focus ring, shadow ring,chamber, susceptor, lift pin, dome, end effector, liner, support,injectorport, manometer port, wafer insert passage, screen plate,heater, vacuum chuck, paddle, process tube, wafer boat, liner, pedestal,long boat, vertical boat, dummy wafer, conditioning pad and waferholder.
 9. A semiconductor processing component as in any of claims 1-3,wherein the inorganic surface comprises a ceramic surface.
 10. Asemiconductor processing component as in any of claims 1-3, wherein thesurface is selected from the group consisting of Si, diamond, Y₂O₃,ZrO₂, SiC, Si₃N₄, AlN, Al₂O₃ and quartz.
 11. A semiconductor processingcomponent as in any of claims 1-3, wherein the surface is a machinedsurface.
 12. A semiconductor processing component as in any of claims1-3, wherein the surface is a vapor-deposited material.
 13. Asemiconductor processing component as in any of claims 1-3, wherein thesurface is a vapor-deposited material selected from the group consistingof CVD Si, CVD SiO₂, CVD SiC, CVD Si₃N₄, CVD diamond, Y₂O₃ and ZrO₂. 14.A process for cleaning a semiconductor processing component having aninorganic surface, the process comprising the steps of: a) exposing theinorganic surface to a solvent having at least 1 v/o of an acid selectedfrom the group consisting of HF, acids having a pKa of less than aboutone, and mixtures thereof, and b) directing a flow of frozen CO₂ pelletsupon the surface.
 15. The process of claim 14, wherein the surface isexposed to the solvent for a time sufficient to provide the surface witha metallic contaminant concentration of at most about 600 ppm, asmeasured by SIMS at a depth of about 10 nm.
 16. The process of claim 14,wherein the surface is exposed to the solvent for a time sufficient toprovide a surface concentration of metal contaminants other thanalkaline and alkaline earth metals of at most about 400 ppm, as measuredby SIMS at a depth of about 10 nm.
 17. The process of claim 14, whereinthe surface is exposed to the solvent for a time sufficient to providethe surface with an iron contaminant concentration of at most about 225ppm, as measured by SIMS at a depth of about 10 nm.
 18. The process ofclaim 14, wherein the surface is exposed to the flow of frozen CO₂pellets for a time sufficient to provide a surface particulatecontamination of at most about 0.4 particles larger than about 0.3 μmper square centimeter.
 19. The process of claim 14, wherein after theflow of frozen CO₂ pellets is directed onto the surface, the componentis installed in a furnace used for processing semiconductor wafers. 20.The process of claim 19, wherein no additional cleaning steps arecarried out between completing the flow of frozen CO₂ pellets andinstalling the component in the furnace.
 21. The process of claim 14,wherein after the flow of frozen CO₂ pellets is directed onto thesurface, the component is sealed in a package suitable for storage andtransport.
 22. The process of claim 21, wherein no additional cleaningsteps are carried out between completing the flow of frozen CO₂ pelletsand packaging the component.
 23. A process as in claim 21 which includesthe further steps of removing the component from the package andinstalling the component into a furnace used for processingsemiconductor wafers.
 24. A process as in claim 23 wherein no additionalcleaning steps are carried out between removing the component from thepackage and installing it into the furnace.
 25. The process of claim 14,wherein prior to the step of exposing the inorganic surface to thesolvent, the component is subjecting to blasting with green SiC.
 26. Theprocess of claim 14, wherein the inorganic surface is selected from thegroup consisting of Si, diamond, Y₂O₃, ZrO₂, SiC, Si₃N₄, AlN, Al₂O₃ andquartz.
 27. The process of claim 14, wherein the inorganic surface has avapor-deposited coating thereon.
 28. The process of claim 14, whereinthe surface is a vapor-deposited material selected from the groupconsisting of CVD Si, CVD SiO₂, CVD SiC, CVD Si₃N₄, CVD diamond, Y₂O₃and Zro₂.
 29. A process for cleaning a semiconductor processingcomponent having an inorganic surface, the process comprising the stepsof: a) exposing the inorganic surface to a solvent comprising an acid,and b) directing a flow of frozen CO₂ pellets upon the surface.
 30. Theprocess of claim 29, wherein no additional cleaning steps are carriedout between steps a) and b).
 31. The process of claim 29, wherein thesolvent has at least 1 v/o of an acid selected from the group consistingof HF, acids having a pKa of less than about one, and mixtures thereof.32. A process for cleaning a semiconductor processing component havingan inorganic surface, the process comprising the steps of: a) blastingwith green SiC particles, and b) directing a flow of frozen CO₂ pelletsupon the surface.
 33. A process for cleaning an inorganic surface of avirgin semiconductor processing component, the surface having a lowlevel of unavoidable metallic impurities thereon, which processcomprises the steps of: a) directing a flow of frozen CO₂ pellets uponthe surface; and b) sealing the component in a package suitable forstorage and transport, wherein no additional cleaning steps are carriedout between completing the flow of frozen CO₂ pellets and packaging thecomponent.
 34. A process as in claim 33 which includes the further stepsof: c) removing the component from the package; and d) installing thecomponent into a furnace used for processing semiconductor wafers.
 35. Aprocess as in claim 34 wherein no additional cleaning steps are carriedout between step c) and step d).
 36. A process for cleaning an inorganicsurface of a virgin semiconductor processing component, the surfacehaving a low level of unavoidable metallic impurities thereon, whichprocess comprises the steps of: a) directing a flow of frozen CO₂pellets upon the surface; and b) installing the component into a furnaceused for processing semiconductor wafers wherein no additional cleaningsteps are carried out between completing the flow of frozen CO₂ pelletsand installing the component.
 37. A process as in any of claims 33-36wherein the cleaning process does not employ an acid cleaning prior tocontacting the workpiece with the frozen CO₂ pellets.
 38. A process asin claim 33 wherein the inorganic surface comprises a vapor depositedcoating.
 39. A process as in claim 36 wherein the inorganic surfacecomprises a vapor deposited coating.
 40. A process as in any of claims14, 29, 32, 33 and 36 wherein the inorganic surface comprises a coatingprovided by chemical vapor deposition, sputter deposition or spraycoating.